This is a panel taken from "The Fall of Sunset Shimmer" story that was released in the San Diego Comic Con exclusive edition of issue 9 of MLP:FIM, which gives a little back-story to Celestia's former student

This shows the uncolored art so that you can better read some of the book titles. Besides the nasty little special edition Sunset is holding in her hoof, one can see references to Fringe, Trek, DC, Shirley Jackson, Steve Martin, even Quantum Leap. This is how I keep myself entertained

For those of you that couldn't get this edition, the story will be reprinted this fall in the one-shot "Equestria Girls" annual.Brush and ink, mechanical pens, Faber Casteel PITT pens on 11x17 Bristol Board

They are not for public access. Sunset Shimmer broke into that room, and when that pony behind the desk saw her she went right to Celestia. The next page in the comic after this shows Celestia saying to Sunset Shimmer that because of what she did right then, she's no longer to be her personal student.